Microelectrodes and microelectrode arrays have been fabricated for use in living tissue for voltammetric analysis of biological fluids. The arrays are made on silicon substrates using the vacuum techniques employed in the electronics industry. These techniques are likely to be less useful in modifying the individual electrodes in an array due to the multiple operations required for each electrode. In contrast, electrochemical modification would allow the individual address of each microelectrode and allow the surface modifications under mild conditions. We propose to investigate a specific approach to the electrochemical modification of microelectrodes with the goal of enhancing the voltammetric response of the electrodes toward specific neurotransmitters and other biologically important substances. This would allow analysis for neurotransmitters and other substances using multiple sensors in a microarray.